Compression release device, especially for internal combustion engines

ABSTRACT

A compression release unit which is purely mechanically operated and comprises a plate insertable into a spring chamber of an internal combustion engine, and in which a wire with a crank and a control arm resilient relative to said crank is hinged to said plate. The said crank when in its compression release position is located below the spring keeper of one valve and in this position forms an angle of from 69* to 45* with said plate.

United States Patent [56] References Cited UNITED STATES PATENTS 12/1952 Goldsmithwm... 1

[721 Inventors Albert A.Weglage;

David E. Weglage. both of Dayton. Ohio 839,357

[21 Appl No.

[22] Filed July 7, 1969 [45] Patented July 6, 1971 [73] Assignee Walter Becker Dayton, Ohio 11 part interest purely into a mechanically operated and comprises a plate insertable 1 1 COMPRESSION RELEASE DEVICE ESPECIALLY spring chamber of an internal combustion engine, and in FOR "S CPMBPSTK ENGINES which a wire with a crank and a control arm resilient relative 15 Clams Drawmg to said crank is hinged to said plate. The said crank when in its [52] US. Cl...... compression release position is located below the 51 keeper of one valve and in this position forms an an 69 to 45 with said plate.

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sum 1 or 2 INVENTORS ALBERT H. lA EGLAGE DAV/D E. WEGLHGE BY 9 z PATENTEU JUL 6 |97| SHEEY 2 BF 2 FIG-8 llaz FIG-IO INVENT R HLBERT A. WEGLHGE DAVID E. bJEGL/IGE COMPRESSION RELEASE DEVICE, ESPECIALLY FOR INTERNAL COMBUSTION ENGINES The present invention relates to internal combustion engines and, more specifically, concerns the manual starting of such engines.

The manual starting of internal combustion engines, especially those used in connection with garden and horticultural implements, such as lawn mowers, snow blowers, pumps and the like, has presented quite some problem, especially when engines of higher horse power,.for instance four horse powers, and higher, are involved. Therefore, numerous attempts have been made to facilitate the manual starting of such engines by reducing the compression in the cylinder during the starting phase.

According to one proposition in this direction, the cam of the cam shaft controlling the valve opening and closing has been changed so as to keep the intake valve open for a longer period of time than normal. While in this way the compression is reduced during the starting phase, this compression loss is maintained during the entire running phase of the engine. Moreover, with this mechanism the valve must close for each cycle so that the compression release is rather limited.

According to another suggestion in this direction, an auxiliary cam is provided which is operative during the starting phase only and is out of operation during the ordinary running period of the engine. Devices of this type are rather expensive and still do not represent a satisfactory solution because in this instance the valve has to close during each revolution of the crankshaft and the starting phase of the engine may begin when the valve is closed or is in nearly closed position.

Therefore, it has been suggested to combine a so-called impulse starter with the crankshaft of an internal combustion engine, which impulse starter is for purposes of starting an engine first cranked up or wound up like a clockwork and then can be released so as to convey the starting force to a cylinder piston system. Such impulse starter, however,'is rather'expensive and its cranking during the last phase of the cranking process requires a considerable effort so that this starting mechanism cannot be used by persons of limited physical ability.

According to still another proposition described in our U.S. Pat. No. 3,330,263, an entirely new concept is employed in this connection inasmuch as the air passing from the crankcase into the spring chamber is made use of for controlling the compression release. While such an arrangement has proved highly successful and inexpensive, it has certain limitations as to the weight of the air-operable control arm forming part of the air-operable compression release member.

It is, therefore, an object of the present invention to provide a compression release mechanism which, while having the advantage of the compression release set forth in our abovementioned U.S. Pat. No. 3,330,263, will be free from the limitations thereof,

It is another object of this invention to provide a compression release mechanism as set forth above, which is purely mechanically operated, i.e. is not air-operated.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing, in which:

FIG. 1 is a vertical section through a customary onecylinder four stroke cycle internal combustion engine equipped with a compression release mechanism according to the invention.

FIG. 2 is a section taken along the line Illl of FIG. 1.

FIGS. 3 and 4 illustrated working phases of the compression release mechanism according to the invention.

FIG. 5 is a perspective view of the compression release device by itself.

FIG. 6 in connection with FIG. 2 shows the holding in operative position of the plate to which the compression release lever means are hinged.

FIGS. 7 to 10 illustrate further modifications of the present invention.

The compression release mechanism according to the present invention consists primarily of at lease one control arm hinged to a plate arranged in the spring chamber and provided with a crank which when occupying its compression releasing position at the standstill of the engine forms with the vertical plane perpendicular to said plate an angle of from 21 to 45, preferably from 23 to 38, while being located below the marginal area of the spring keeper.

When a downward pressure is exerted on the said crank, the said control arm is spring-loaded and springs back to an increased extent when the pressure on the crank is temporarily relieved so that the arm springs upwardly to such an extend that the crank moves completely out of the path of the spring keeper. While the engine is running, the said arm has the tendency to swing the crank back into the path of the spring keeper. However, the reciprocatory movement of the spring keeper is, even at idling speed, too fast for such return movement of the crank so that the crank does not interfere with the normal operation of the respective valve with which the compression release mechanisms is associated. Only when the engine speed drops below idling speed, will the reciprocating movement of the said spring keeper become so slow that the said arm is able to swing said crank back below the spring keeper, thereby preventing the valve pertaining to the spring keeper from closing. In other words, the valve is now kept open by the crank and held in this position which represents the compression release position of the valve.

In order to make the movement of the crank into its compression releasing position more instantaneous and positive, the said crank is in conformity with a further development of the invention provided with a second or auxiliary arm acting as added weight to said control arm.

According to a still further development of the present invention, the control arm has its outer end bent downwardly with regard to the remainder of the arm so as to form an obtuse angle therewith. This imparts a greater resiliency and spring-back upon said control arm when a downward pressure is exerted by the spring keeper upon the crank in response to the starting of the engine.

In operation, the compression release mechanism according to the present invention differs from the compression release mechanism according to our above-mentioned U.S. Pat. No. 3,330,263 primarily in that its operation is purely mechanical and is due to the resiliency of the control arm in combination with the crank and is not at all dependent on the air passing from the crankcase into the spring chamber. Consequently, the limitation as to the weight of the control arm does not exist with the compression release mechanism according to the invention so that a heavier wire or arm can be used which will permit a considerably increased compression release since it is no longer a problem to lift the crank out of the path of the reciprocating spring keeper and later to return the crank into the path of the reciprocating spring keeper when the engine drops below its idling speed.

Referring now to the drawings in detail, the internal combustion engine illustrated therein may, for instance, be of the general type shown in FIG. 6 of our above-mentioned U.S. Pat. No. 3,330,263. The internal combustion engine shown in FIG. 1 comprises a cylinder block 1 with a cylinder la. Mounted on cylinder block 1, in customary manner, is a cylinder head 1b. Cylinder block 1 comprises a spring chamber 2 which has connected thereto a housing or crankcase 3. Journaled on said housing 3 is a cam shaft 4 which is drivingly connected to the crankshaft (not shown) of the engine through gears in a manner customary with four-stroke cycle internal combustion engines. As is also well known in the art, said cylinder 2 has reciprocably mounted thereon a piston (not shown) which is drivingly connected to the crankshaft.

Likewise in customary manner, cam shaft 4 is provided with a first cam 5 and a second cam 6. Cam 5 normally, i.e. during idling and the ordinary driving operation of the engine, is in continuous engagement with a lifter 7 having a lifter shank 7a, which in turn engages the stem 8 of the exhaust valve 9 controlling the connection of the engine cylinder with an exhaust port (not shown) through a passage la. As will also be seen from FIG. 1, that portion of valve stem 8 which extends into the spring chamber 2 is surrounded by a valve spring 10 having one end resting against spring chamber wall 11. The other end of spring 10 rests against a spring keeper 12 holding spring 10 under preload and being held in its position by a C-washer 13 which rests in a recess of 14 of spring keeper l2 and engages a groove 80 in the valve stem 8. Clamps of this type are well known and one C-washer is shown in FIG. 3 of our abovementioned US. Pat. No. 3,330,263. As will be evident from the above, spring 10 continuously urges valve 9, shown in an open pressure releasing position, into its closing position.

Cylinder block 1 furthermore, in customary manner, comprises a lifter l5 controlled by a cam 6 on cam shaft 4. Cam 6 in turn through lifter shank 15a and valve shank 16 controls the inlet valve 17 which latter controls a passage 17a communicating with a fuel supply passage 17b. Similar to the outlet valve 9, also the inlet valve 17 is provided with a spring 18 located in the spring chamber 2. A spring keeper l9 and a C- washer (not shown) but corresponding to C-washer 13 hold the spring 18 under preload, said spring 18 continuously urging inlet valve 17 into closing position.

In conformity with the standard design of four stroke cycle internal combustion engines employed for agricultural and horticultural implements such as lawn mowers, the spring chamber 2 communicates with the interior of the housing or crankcase 3 through a passage 21 through which during the operation of the engine a gaseous fiow occurs from the crankcase to the spring chamber 2 from where it is released, for instance, through a breather plate of any standard design as, for example, of the type shown in FIGS. 12 and I24 of our abovementioned US. Pat. No. 3,307,527. Such breather plate B is also shown in FIGS. 2 and 6 of the attached drawings.

The arrangement described so far is substantially standard with four stroke cycle internal combustion engines if they are I employed, for instance, with rotary lawn mowers, snow blowers, and pumps. The present invention is characterized by a pressure release system and unit as it will now be described.

Referring to FIG. 5 showing an embodiment of a pressure release unit according to the invention, the pressure release unit shown therein comprises a first plate 22 which is completely flat and has a second plate 23 connected thereto in any convenient manner, preferably by spot welding. The second plate 23 which in the showing of FIG. 5 forms the top plate is provided with a long bead generally designated 24 from which sections have been cut away so that only sections 24a, 24b and 240 remain. In addition thereto, plate 23 is provided with a second and very short bead 25. Beads 24a and 25 serve for firmly holding the composite plate 22, 23 in the engine and more specifically in the spring chamber 2, as will be explained further below.

Due to the cut away portions between the bead sections 24a and 24b on one hand and 24b and 24c on the other hand, gaps are formed betweenthe bead sections 24a and 24b and also between 24b and 24c. Furthermore, the top plate sections between bead sections 24a and 24b and between bead sections 24b and 24c are cut away leaving grooves 24', 24". The bead sections 24b and 24c form together with the adjacent portion of the bottom plate 22 hinges for a wire 26 which extends through said bead sections 2412 and 240 and has a first arm 26a and a second arm 26b. The wire portion extending through bead sections 24b, 240 comprises between these two bead sections a loop or crank 260 which is adapted to be acted upon by the spring keeper 12 as will be explained further below. Arm 260 preferably has a bend b so that the arm 26a forms an obtuse angle as can best be seen from FIGS. 1, 3 and 4. In other words the arm 26a when leaving the gap between the bead sections 240 and 24b will when the outer free end touches the spring chamber wall lla have one arm section going up at an -acuteangle with regard to the top surface of the plate 23 up to the bend b and will have another arm section from said bend b going downwardly while forming an obtuse angle with the first arm section. When the front portion of arm 26a is pressed against the spring chamber wall Ila the arm 26a temporarily yields (the obtuse angle formed by the two arm sections temporarily increases slightly), and springs back away from the spring chamber wall 11a when the downward pressure on arm 26a ceases.

When the crank section 26c occupies its normal compression release position during the standstill of the engine, the angle defined by the plane through the two legs of the loop or crank section 260 with the substantially plane top surface of the plate 23 or the spring chamber wall 11a is within the range of from 69 to 45, preferably from 67 to 52. The arm 26b may be located outside the plate 23 and merely adds weight to the arm 26a for a purpose which will be described in connection with the operation of the compression release system according to the invention. Therefore arm 26b does not have to touch the spring chamber wall 11a. However, in some cases, where additional spring action is desired, it may be advantageous to have the free end of arm 26b touch the wall 11a somewhat similar to arm 260. While wires of various thicknesses may be employed for the wire 26, a wire having a thickness of 0.069 inch has proved highly satisfactory for the present invention.

It will also be noted from FIG. 5 7plate 22, 23 is provided with a cutout 28for the push rod [50 indicated in FIG. 5 by a dot-dash circle, andfurther has a bore 27 slide fit for the push rod 7a. This cutout 28 is such as to permit a free slidethrough movement of the push rod 15a. Thus, when the composite plate 22, 23 is placed upon the spring chamber wall 11a which in the embodiment of FIG. I represents the bottom of the spring chamber 2, so that push rod 7a extends through bore 27 and push rod is located in sliding engagement with the edge of the cutout 28, the plate 22, 23 is properly located.

After the plate 22, 23 is thus properly located, it is firmly held in the spring chamber 2 by the breather plate B which has a slight bevel 29 (see FIG. 6) which engages and partially extends over the beads 24a and 25 as is clearly evident from FIG. 2. In this way the composite plate 22, 23 is firmly held in the springchamber against the wall 11a thereof. Furthermore, the plate 22, 23 is originally so installed that the free end of arm 26a touches the wall 11a of the spring chamber 2 while the crank or loop 260 is below the marginal area-of the spring keeper as shown in FIG. 1. In this positionthe crank or loop 26c lifts the valve 8, 9 of the valve seat to the desired maximum extent for compression release purposes. As an example the valve 9 which likewise merely by way of example be the exhaust valve, may at its maximum compression rglease be lifted off its seat, for instance, by 0.100 inch or more.

OPERATION It may be assumed that the compression release unit of FIG. 5 has been properly installed in the spring chamber 2 in the manner described above and that the engine is at a standstill while the wire 26 with the outer free end of the arm 26a engages the' spring chamber wall 110, whereas the crank 26c occupies the position shown in FIG. 1 below the spring keeper 12 so that the valve 9 is lifted off its seat and occupies its compression release position. When the engine is now started, for instance, in a manner conventional with engines for lawn mowers, snow blowers, pumps, or the like, by pulling a rope wound around a pulley keyed to the crankshaft, the cam shaft 4 is turned at a minimum resistance since the compression in the cylinder of the engine is relieved inasmuch as practically no compression is encountered in the cylinder as long as the crank 26b occupies its FIG. 1 position below the spring keeper 12. The engine, therefore, gains momentum so that the piston due' to ir iertia moves back and forth several times with the result that the cam 5 lifts the valve 9 to the maximum extend and the spring 10 tends to close the valve 9. Due to this momentum, the valve shank 8 through the intervention of the spring keeper 12 exerts a fast impact upon the crank 260 so as to impart upon the same a slight bend as a result of which the spring arm 26a will have its arm sections spread somewhat as shown on an exaggerated scale in solid lines in FIG. 3, in other words the obtuse angle formed by the arm sections of arm 26a is increased. This imparts upon the arm 260 a spring action or expressed differently loads the arm 26a similar to loading a spring. As soon as the cam 5 on cam shaft 4 through the intervention of the lifter rod 7a lifts the valve 8, 9 and thereby lifts the spring keeper 12 off the crank 260, the spring action imparted upon the arm 26a causes the arm 26a to spring back as shown in dash lines in FIGS. 3 and 4 so that the crank 260 is moved out from below the spring keeper 12 with the result that now the valve 9 can close and compression builds up in the cylinder. This is followed by an ignition and the engine is running. It will be appreciated in this connection that when the operator pulled the rope for starting the engine, the compression release was effective so that the operator did not encounter any material resistance and was thus able to cause the piston quickly to move up and down. After the operator at the end of his rope pulling action releases the pull rope, the engine had gained sufficient momentum to overcome the compression being built-up in the engine after the crank 26c has moved out from below the spring keeper 12 with the subsequent ignition as outlined above.

After the arm 26a has been lifted off the spring chamber wall 11a to such an extend that the crank 26c occupies its full line position shown in FIG. 4, the weight of the arm 26a increased by the weight of the arm 26b will have the tendency to move the crank 260 back below the spring keeper 12. How ever, the movement of the spring keeper 12 during the running of the engine even at idling speed is so fast that the crank has no chance to again get below the spring keeper 12. As shown in FIG. 4 in dash lines the lower end of spring keeper l2 prevents the crank 260 from getting below the spring keeper. In other words at best the crank 26c can move back and forth from its solid position shown in FIG. 4 to its dash line position shown in FIG. 4. However, when the engine speed drops below idling speed, thereby considerably slowing down thereciprocatory movement of spring keeper 12, the relatively heavy composite weight of both the arm 26a and arm 26!; will be able to move the crank 26: below the spring keeper 12 back into the position shown in FIG. 1. As a result thereof the crank 260 now again holds up the spring keeper 12 whereby (since the spring keeper is locked to valve stem 8 by the C-washer 13) the valve 9 is prevented from closing, in other words is retained in its lifted or compression release position so that when the engine comes to a standstill the valve 9 occupies its compression release position. In this way the en gine is ready for a new effortless starting.

While the compression release unit 22-27 illustrated in FIGS. 1 to 5 represents the preferred form of the present invention, it is by no means limited thereto. Thus, instead of providing the arm 26b as additional weight to the weight of the arm 26a to aid the latter in quickly and instantaneously returningthe crank 260 to a position underneath the spring keeper 12 when the engine speed drops below idling speed, the arm 26b may also be omitted and instead an additional weight, for instance, in the form of solder may be added to arm 26a as shown in F IG. 7.

Another way of adding weight to arm 26a while omitting arm 26b would be by putting a hair pin bend in arm 260 as shown in FIG. 8.

Furthermore, as shown in FIGS. 2 and 5, the arm 26a extends over a narrow marginal portion of the bore 21. Since the wire 26 and more specifically the arm 26a is, in contrast to the arrangement of our US. Pat. No. 3,330,263, not actuated by air passing through the bore 21 into the spring chamber 2, the arm 26a may also be arranged completelylaterally of the bore 21 as shown in FIG. 9. The reason why the arrangement of FIGS. 2 and 5 with the arm 26a extending over a marginal area of bore 21 is preferred is merely of a nature to facilitate the production of the compression release unit as shown in FIGS. 2 and 5. More specifically, to assure an easy movement of the wire 26 in the hinges formed by the bead sections 24!) and 24c and to prevent any binding of the wire arm 26a where it leaves the gap between the bead sections 24a and 24b, that portion of the upper plate 23 which lies between the gap 25a and the bore 21 is cut out so that a groove 30 is formed, the bottom of which is formed by the top surface of the bottom plate 22. This groove is preferably wider than the diameter of the wire arm 2611 so that the wire portion within the bead sections 24b, 24c can slightly move in the longitudinal direction of said bead section. For the same reason also the gap between the bead sections 24b and 24c is slightly wider than the distance between the legs of the crank 240. Thus, a binding of the wire in the bead sections and a binding of the arm 260 at the bend 26' will, for all practical purposes, be impossible.

According to still another modification shown in the drawings, the arm 260 may be replaced by a straight arm as shown in FIG. 10. In this instance the arm 26a will rest on the outer edge portion 21' of the bore 21. The arm effective for the spring action is, of course, considerably shorter than in the preferred embodiment of FIGS. 2 and 5 and therefore while working in some instances might not always work' under all circumstances.

It is, of course, also to be understood that the device of the present invention will also work when arm 26a get the shape of arm 26b and arm 26b gets the shape of arm 260.

It will be appreciated that the strength of the wire 26 may vary in conformity with the respective springs 10, ie the force exerted thereby. However, as a mere specific example, the spring 10 may be a spring having ll lbs. 10 02. at 0.239 deflection. The spring could have a tolerance of :5 lbs. The compression release wire as shown in FIGS. 2 and 6 may have a thickness of 0.069 inch with the arm 26a having a longer arm section of a length of l-l l/ 16 inches and a shorter arm section (which touches the spring chamber wall 11a) of a length of one-half inch. The other arm 26b may in this instance have a length of l-% inches. The crank 26c may have a width of 5/16 inch and a height of 9/32 inch.

The distance between the axis of the bore 27 for the push rod and the axis of the bead 24 would in these circumstances be 0.407 with the maximum amount oflift by the crank equaling 0.265 inch.

It is, of course, obvious that this distance will vary with the travel of the respective valve as controlled by the pertaining cam. However, the important thing to bear in mind is that the said distance must be such that the crank 260 will in conformity with the spring impacted upon the spring keeper through the crank upon the respective arm, e.g. 26a, move out from below the spring keeper in the manner described above under the heading "Operation."

It is, of course, to be understood that the present invention is, by no means, limited to the particular designs shown in the drawings, but also comprises any modifications within the scope of the appended claims.

It is also to be understood that while the compression release of the present invention has been described in connection with the exhaust valve, it will work equally well when instead it is used in connection with the inlet valve.

It may furthermore be mentioned that in the compression release unit the arm means instead of extending in the direction shown in the drawings may also extend in the opposite direction without affecting the principle of the invention, in other words, the unit would be an image of the showing in the drawings as far as the entire wire including crank and arm means is concerned.

What we claim is:

l. A four stroke cycle internal combustion engine, which includes: spring chamber means, inlet and outlet valve means movable from an open to a closed position and vice versa, each one of said inlet and outlet valve means comprising a shank extending into said spring chamber means, two spring keeper means arranged in said spring chamber means and respectively connected to said shanks of said inlet and outlet valve means, spring means respectively surrounding said shanks and continuously urging the pertaining valve means to move to the closed position thereof, lifter means extending into said spring chamber means and being respectively substantially axially aligned with and operable to actuate said shanks, a rotatable cam shaft for controlling said lifter means, plate means secured in said spring chamber means and having one of its larger surfaces located opposite said spring keeper means, a wire hinged to said plate means and having a U- shaped crank movable to a first position in the path of movement of one of said spring keeper means to prevent the per taining valve means from closing and also movable from said first position to a second position out of the path of movement of said one spring keeper means to permit said pertaining valve means to close in the normal course of the engine cycle, said crank when in said first position at a stand-still of said engine forming with said one larger surface of said plate means an angle within the range of from 69 to 45, and resilient arm means forming part of said wire and adapted in response to said one spring keeper means impacting upon said crank at an engine speed at least as high as the engine idling speed to be spring loaded so as to move said crank from said first position to said second position out of the path of movement of said one spring keeper means when said one spring keeper means moves away from said crank, said wire being operable in response to said engine speed dropping below its idling speed to automatically return said crank from a position out of the path of movement of the respective spring keeper means into the path of movement of the latter.

2. An engine according to claim 1, in which said plate means comprises bead means, and in which there is provided a wall member detachably connected to said engine and forming a wall portion of said spring chamber means while being provided with a beveled portion extending into said spring chamber means in holding engagement with said bead means.

3. A compression release unit for insertion into the spring chamber of a four stroke cycle internal combustion engine, which includes: plate means having a first surface and an oppositely located second surface and also having means for orienting said plate means when the latter is being inserted into the spring chamber of a four stroke cycle internal combustion engine, said plate means also including hinge means, and a wire pivotally supported in said hinge means and comprising a crank arranged adjacent to said first surface and movable into a first position representing the compression release position and also movable into a second position representing its ineffective position, said crank when in said compression release position forming with a plane extending from an edge of said plate means adjacent said hinge means to the oppositely located edge of said plate means an angle within the range of from 69 to 45, and a control arm integral with and resiliently connected to said wire so as to urge said crank when the latter is in its second position to move to its first position.

4. A compression release unit for insertion into the spring chamber of a four stroke cycle internal combustion engine, which includes: plate means having a first surface and an oppositely located second surface with a substantially plane surface portion and also having means for orienting said plate means when the latter is being inserted into the spring chamber of a four stroke cycle internal combustion engine, said plate means also including hinge means, and a wire pivotally supported in said hinge means and comprising a crank arranged adjacent to said first surface and movable into a first position representing the compression release position and also movable into a second position representing its ineffective position, said crank when in said compression release position forming with said substantially plane surface portion of said second surface an angle within the range of from 69 to 45, and a control arm integral with and resiliently connected to said wire and extending over at least a portion of said first surface in a direction transverse to the pivot axis of said wire.

5. A compression release unit according to claim 4, in which said angle formed by said crank in its compression release position with said substantially plane surface portion of said second surface is within the range of from 67 to 52.

6. A compression release unit according to claim 3, which includes an auxiliary arm extending in the same direction as said control arm and connected to said wire to aid the force of gravity of said control arm.

7. A compression release unit according to claim 3, in which said crank is U-shaped and open toward said plate.

8. A compression release unit according to claim 3, in which said orienting means include a bore through said plate means for slide-fit engagement with a lifter portion pertaining to a first lifter of the internal combustion engine with which the compression release is to be used, said orienting means also including a cutout for slide-fit engagement with a lifter portion of a second lifter pertaining to the same internal combustion engine to which said first lifter pertains.

9. A compression release unit according to claim 3, in which said control arm has a first section adjacent said wire in said hinge means and also has a second section forming an obtuse angle with said first section while protruding beyond said plate means.

10. A compression release unit according to claim 9, in which said second section has a bent-back portion forming a hairpin bend to increase the weight of said control arm.

11. A compression release unit according to claim 4, in which said plate means is provided with-a cutout extending from said hinge means in alignment with and over a portion of the length of said control arm.

12. A compression release unit according to claim 3, in which said plate means comprises two superimposed substantially plane plates firmly connected to each other, the plate forming said first surface having beads protruding away from the other plate while forming therewith said hinge means.

13. A compression release unit according to claim 12, in which said plate with said first surface has a first auxiliary bead in axial alignment with the beads forming said hinge means and also has a second auxiliary bead in spaced relationship to and on the same side of said plate means as said first auxiliary bead.

14. A compression release unit according to claim 12, in which said plate which forms said first surface is provided with a cutout extending from said hinge means and in alignment with a portion of said control arm.

15. A compression release unit according to claim 3, in which an additional weight is connected to said control arm. 

1. A four stroke cycle internal combustion engine, which includes: spring chamber means, inlet and outlet valve means movable from an open to a closed position and vice versa, each one of said inlet and outlet valve means comprising a shank extending into said spring chamber means, two spring keeper means arranged in said spring chamber means and respectively connected to said shanks of said inlet and outlet valve means, spring means respectively surrounding said shanks and continuously urging the pertaining valve means to move to the closed position thereof, lifter means extending into said spring chamber means and being respectively substantially axially aligned with and operable to actuate said shanks, a rotatable cam shaft for controlling said lifter means, plate means secured in said spring chamber means and having one of its larger surfaces located opposite said spring keeper means, a wire hinged to said plate means and having a U-shaped crank movable to a first position in the path of movement of one of said spring keeper means to prevent the pertaining valve means from closing and also movable from said first position to a second position out of the path of movement of said one spring keepEr means to permit said pertaining valve means to close in the normal course of the engine cycle, said crank when in said first position at a stand-still of said engine forming with said one larger surface of said plate means an angle within the range of from 69* to 45*, and resilient arm means forming part of said wire and adapted in response to said one spring keeper means impacting upon said crank at an engine speed at least as high as the engine idling speed to be spring loaded so as to move said crank from said first position to said second position out of the path of movement of said one spring keeper means when said one spring keeper means moves away from said crank, said wire being operable in response to said engine speed dropping below its idling speed to automatically return said crank from a position out of the path of movement of the respective spring keeper means into the path of movement of the latter.
 2. An engine according to claim 1, in which said plate means comprises bead means, and in which there is provided a wall member detachably connected to said engine and forming a wall portion of said spring chamber means while being provided with a beveled portion extending into said spring chamber means in holding engagement with said bead means.
 3. A compression release unit for insertion into the spring chamber of a four stroke cycle internal combustion engine, which includes: plate means having a first surface and an oppositely located second surface and also having means for orienting said plate means when the latter is being inserted into the spring chamber of a four stroke cycle internal combustion engine, said plate means also including hinge means, and a wire pivotally supported in said hinge means and comprising a crank arranged adjacent to said first surface and movable into a first position representing the compression release position and also movable into a second position representing its ineffective position, said crank when in said compression release position forming with a plane extending from an edge of said plate means adjacent said hinge means to the oppositely located edge of said plate means an angle within the range of from 69* to 45*, and a control arm integral with and resiliently connected to said wire so as to urge said crank when the latter is in its second position to move to its first position.
 4. A compression release unit for insertion into the spring chamber of a four stroke cycle internal combustion engine, which includes: plate means having a first surface and an oppositely located second surface with a substantially plane surface portion and also having means for orienting said plate means when the latter is being inserted into the spring chamber of a four stroke cycle internal combustion engine, said plate means also including hinge means, and a wire pivotally supported in said hinge means and comprising a crank arranged adjacent to said first surface and movable into a first position representing the compression release position and also movable into a second position representing its ineffective position, said crank when in said compression release position forming with said substantially plane surface portion of said second surface an angle within the range of from 69* to 45*, and a control arm integral with and resiliently connected to said wire and extending over at least a portion of said first surface in a direction transverse to the pivot axis of said wire.
 5. A compression release unit according to claim 4, in which said angle formed by said crank in its compression release position with said substantially plane surface portion of said second surface is within the range of from 67* to 52*.
 6. A compression release unit according to claim 3, which includes an auxiliary arm extending in the same direction as said control arm and connected to said wire to aid the force of gravity of said control arm.
 7. A compression releaSe unit according to claim 3, in which said crank is U-shaped and open toward said plate.
 8. A compression release unit according to claim 3, in which said orienting means include a bore through said plate means for slide-fit engagement with a lifter portion pertaining to a first lifter of the internal combustion engine with which the compression release is to be used, said orienting means also including a cutout for slide-fit engagement with a lifter portion of a second lifter pertaining to the same internal combustion engine to which said first lifter pertains.
 9. A compression release unit according to claim 3, in which said control arm has a first section adjacent said wire in said hinge means and also has a second section forming an obtuse angle with said first section while protruding beyond said plate means.
 10. A compression release unit according to claim 9, in which said second section has a bent-back portion forming a hairpin bend to increase the weight of said control arm.
 11. A compression release unit according to claim 4, in which said plate means is provided with a cutout extending from said hinge means in alignment with and over a portion of the length of said control arm.
 12. A compression release unit according to claim 3, in which said plate means comprises two superimposed substantially plane plates firmly connected to each other, the plate forming said first surface having beads protruding away from the other plate while forming therewith said hinge means.
 13. A compression release unit according to claim 12, in which said plate with said first surface has a first auxiliary bead in axial alignment with the beads forming said hinge means and also has a second auxiliary bead in spaced relationship to and on the same side of said plate means as said first auxiliary bead.
 14. A compression release unit according to claim 12, in which said plate which forms said first surface is provided with a cutout extending from said hinge means and in alignment with a portion of said control arm.
 15. A compression release unit according to claim 3, in which an additional weight is connected to said control arm. 